1. Field of Invention
The present invention relates to metal-air fuel cell battery systems designed to produce electrical power from metal-fuel tape transported over the cathode structures of the system, and more particularly to such systems employing movable cathode structures having low friction characteristics.
2. Brief Description of the Prior Art
In copending U.S. application Ser. No. 08/944,507 entitled "High-Power Density Metal-Air Fuel Cell Battery System, Applicants disclose several types of novel metal-air fuel cell battery (FCB) systems. During power generation, metal-fuel tape is transported over a stationary cathode structure in the presence of an ionically-conductive medium, such as an electrolyte-impregnated gel (i.e. electrolyte-impregnated film). In accordance with well known principles of electro-chemistry, the transported metal-fuel tape is oxidized as electrical power is produced from the system.
FCB power generation systems of the type disclosed in U.S. application Ser. No. 08/944,507 have numerous advantages over prior art electro-chemical power generation devices including, for example, the generation of electrical power over a range of output voltage levels selectable to particular electrical load conditions. Also, the oxidized metal-fuel tape can be reconditioned (i.e. recharged) during battery charging cycles carried out during electrical power generation, as well as separately therefrom.
In copending application Ser. No. 09/074,337 entitled "Metal-Air Fuel-Cell Battery Systems" filed May 7, 1998, Applicants disclose several novel systems and methods for reconditioning oxidized metal-fuel tape used in FCB systems. In theory, such technological improvements enable metal-fuel tape to be quickly recharged in an energy efficient manner for reuse in electrical power generation cycles. Such advances offer great promise in many fields of endeavor requiring electrical power.
The greatest limitation, however, with prior art metal-air FCB systems is that, as the metal-fuel tape is being transported over the stationary cathode structures within such systems, frictional (e.g. shear) forces are generated, causing a number of problems to arise.
One problem is that such frictional forces cause an increase in the amount of electrical power required to transport the metal-fuel tape through the system.
Another problem is that such frictional forces cause metal-oxide particles to be shed from metal-fuel tape during transport and to become embedded within the porous structure of the cathode, thereby preventing ionic transport between the cathode and ionically-conductive medium (i.e. referred to as "blinding"), and increasing the likelihood of damage (or destruction) to the surface of the cathode structure and metal-fuel tape.
Overall, such problems tend to reduce the operational efficiency of prior art metal-air FCB systems, as well as the life of the cathode structures and metal-fuel tape employed therein.
Thus, there is a great need in the art for an improved metal-air fuel cell battery system which avoids the shortcomings and drawbacks of prior art systems and methodologies.